thumb|Panicum miliaceum ([[MHNT)]]

Panicum miliaceum is a grain crop with many common names, including proso millet, broomcorn millet, common millet, hog millet, Kashfi millet, red millet, and white millet. Archaeobotanical evidence suggests millet was first domesticated about 10,000 BP in Northern China. Major cultivated areas include Northern China, Himachal Pradesh of India, Nepal, Russia, Ukraine, Belarus, the Middle East, Turkey, Romania, and the Great Plains states of the United States. The crop is notable both for its extremely short lifecycle, with some varieties producing grain only 60 days after planting, and its low water requirements, producing grain more efficiently per unit of moisture than any other grain species tested. The name "proso millet" comes from the pan-Slavic general and generic name for millet (, , , ).

Proso millet is a relative of foxtail millet, pearl millet, maize, and sorghum within the grass subfamily Panicoideae. While all of these crops use C4 photosynthesis, the others all employ the NADP-ME as their primary carbon shuttle pathway, while the primary C4 carbon shuttle in proso millet is the NAD-ME pathway.

Evolutionary history

Panicum miliaceum is a tetraploid species with a base chromosome number of 18, twice the base chromosome number of diploid species within its genus Panicum. The species appears to be an allotetraploid resulting from a wide hybrid between two different diploid ancestors. One of the two subgenomes within proso millet appears to have come from either P. capillare or a close relative of that species. The second subgenome does not show close homology to any known diploid Panicum species, but some unknown diploid ancestor apparently also contributed a copy of its genome to a separate allotetraploid species P. repens (torpedo grass). However, the species has experienced only limited amounts of fractionation and copies of most genes are still retained on both subgenomes. A 2018 report developed a morphometric analysis method which distinguishes seeds of P. miliaceum and P. ruderale on the basis of micromorphology.

Domestication and history of cultivation

thumb|right|upright=2.0|Map of the world showing approximate centers of origin of agriculture and its spread in prehistory: the Fertile Crescent (11,000 BP), the Yangtze and Yellow River basins (9,000 BP), the New Guinea Highlands (9,000–6,000 BP), Central Mexico (5,000–4,000 BP), Northern South America (5,000–4,000 BP), sub-Saharan Africa (5,000–4,000 BP, exact location unknown), and eastern North America (4,000–3,000 BP).

Weedy forms of proso millet are found throughout central Asia, covering a widespread area from the Caspian Sea east to Xinjiang and Mongolia. These may represent the wild progenitor of proso millet or feral escapes from domesticated production. Indeed, in the United States, weedy proso millet, representing feral escapes from cultivation, are now common, suggesting current proso millet cultivars retain the potential to revert, similar to the pattern seen for weedy rice. Currently, the earliest archeological evidence for domesticated proso millet comes from the Cishan site in semiarid north east China around 8,000 BCE. Archaeological charred grains of common millet were found in several Neolithic sites in Europe and Transcaucasia but radiocarbon dates obtained thanks to AMS method directly from the grains, indicated that it appeared in that area in the 2nd millennium BC. At around 1700 BCE, broomcorn millet was present north of the Black Sea, 1450 BCE in central Europe, and 1200 BCE in northern Europe.

Cultivation

Proso millet is a relatively low-demanding crop, and diseases are not known; consequently, it is often used in organic farming systems in Europe. In the United States, it is often used as an intercrop. Thus, proso millet can help to avoid a summer fallow, and continuous crop rotation can be achieved. Its superficial root system and its resistance to atrazine residue make proso millet a good intercrop between two water- and pesticide-demanding crops. The stubbles of the last crop, by allowing more heat into the soil, result in a faster and earlier millet growth. While millet occupies the ground, because of its superficial root system, the soil can replenish its water content for the next crop. Later crops, for example, a winter wheat, can in turn benefit from the millet stubble, which act as snow accumulators. P. miliaceum is commonly classified into five races, miliaceum, patentissimum, contractum, compactum, and ovatum.

Climate and soil requirements

Due to its C4 photosynthetic system, proso millet is thermophilic like maize, so shady locations of the field should be avoided. It is sensitive to temperatures lower than . Proso millet is highly drought-resistant, which makes it of interest to regions with low water availability and longer periods without rain. The soil should be light or medium-heavy. Due to its flat root systems, soil compaction must be avoided. Furthermore, proso millet does not tolerate soil wetness caused by dammed-up water.

Seedbed and sowing

The seedbed should be finely crumbled as for sugar beet and rapeseed.

;Seedling pests

  • shoot fly Atherigona pulla (proso millet shoot fly, a major pest in India and Africa)
  • Atherigona miliaceae, Atherigona soccata, and A. punctata
  • wheat stem maggot Meromyza americana occurs in the United States
  • thrip, Haplothrips aculeatus
  • armyworms Mythimna separata, M. unipuncta, Spodoptera exempta, and S. frugiperda
  • field cricket Brachytrupes sp.

;Stem borers

  • Chilo partellus, Ch. suppressalis, Chilo orichalcociliellus, Sesamia inferens, S. cretica, and Ostrinia furnacalis

;Leaf feeders

  • leaf folders Cnaphalocrocis medinalis and Cn. patnalis
  • hairy caterpillar Spilosoma obliqua
  • rice butterfly Melanitis leda ismene
  • Moroccan locust Dociostaurus maroccanus
  • migratory locust Locusta migratoria
  • grasshoppers Hieroglyphus banian and Oxya chinensis

;Earhead feeders

  • cotton boll worm Helicoverpa zea (in the United States)

;Other pests

  • aphid Sipha flava (in North America)
  • earhead bug Leptocorisa acuta and green bug Nezara viridula suck the milky developing grains in India
  • termites, Odontotermes spp. and Microtermes spp., are the common species recorded on proso millet during dry seasons in India.

Harvesting and postharvest treatments

Harvest time is at the end of August until mid-September. Determining the best harvest date is not easy because all the grains do not ripen simultaneously. The grains on the top of the panicle ripen first, while the grains in the lower parts need more time, making compromise and harvest necessary to optimize yield. Historically grown as animal and bird seed, as of 2020, it has found a market as an organic gluten-free grain.

Proso millet is one of the few types of millet not cultivated in Africa.

Uses

thumb|Cooked rice with proso millet

Nutrition

Millet flour is 9% water, 75% carbohydrates, 11% protein, and 4% fat. In a reference amount of , millet flour supplies 382 calories, and is a rich source (20% or more of the Daily Value, DV) of several B vitamins and dietary minerals.

The demand for more diverse and healthier cereal-based foods is increasing, particularly in affluent countries. Protein content in proso millet grains is comparable with that of wheat, but the proportion of certain essential amino acids (leucine, isoleucine, and methionine) is substantially higher in proso millet.

In the United States, proso millet is used to brew gluten-free beer, being mixed with other grains for texture.

Livestock and poultry

Proso millet is primarily grown as livestock and poultry fodder. As food it is very deficient in lysine and needs complementation. Proso millet is also a poor fodder due to its low leaf-to-stem ratio and a possible irritant effect due to its hairy stem. Foxtail millet, having a higher leaf-to-stem ratio and less hairy stems, is preferred as fodder, particularly the variety called moha, which is a high-quality fodder.

Fermentation products

Starch derived from millet has been shown to be a good substrate for fermentation and malting with grains having similar starch contents as wheat grains. One study suggested that starch derived from proso millet can be converted to ethanol with an only moderately lower efficiency than starch derived from corn. As proso millet is compatible with low-input agriculture, cultivation on marginal soils for biofuel production may present a new market for farmers.